Page:The New International Encyclopædia 1st ed. v. 15.djvu/358

PAPER. iiient work done that tlie early machines differ ill minor details only from the most modern iuachine running to-day.

Earliest Peocess of JIaxufactuke. The method of manufacturing paper by hand from the inner bark of the paper mulberry, as prac- ticed to-day by the Japanese, probably represents the method in vogue from the very earliest times. It is of interest not only on account of its antiquity, but because it presents in outline all other methods, which merely are adaptations of the processes here described. . sheet of paper is an artificially felted web of vegetalile fibre, jniri- fied of perishable materials, so that the remaining fibres are more or less pure cellulose (q.v. ). The process may be described as collecting the raw material, cleaning it by boiling jitli lye, macerat- ing it to a fine pulp, diluting with water, form- ing a sheet on a porous surface (that the water may drain off), and drying the sheet of paper thus formed. The Japanese strip the paper mulberry of its bark, soak it in water till soft enough to strip the outer bark, then separate the inner bark, dry in the sun, and boil with lye obtained by leaching wood ashes. After being well washed, the bark is now beaten into pulp by four men seated around a board of hard wood on which the bark is placed. The men pound with long wooden mallets and turn out each day about 80 pounds of l)ulp per man. The fibre is now mixed with suliicient water, and the sheet of paper formed on a sieve made of fine strips of bamboo. A wooden frame is fitted on the sieve to hold the right amount of liquid pulp. This elevated border is called in Europe the 'deckel,' and prevents the pulp from spread- ing beyond the limits of the sheet. After dipping the sieve into the vat of pulp, the paper- maker dexterously shakes the mold in all directions as the water drains off, thus felting the fibres in all directions and making a strong sheet. The sheets are then spread out on a board and dried in the sun.

The European method of making paper by hand differs in several respects from the Japan- ese. The raw material used (originally linen rags) is too tenacious to be reduced to pulp by hand power, and the earliest European mills used a sort of trip-hammer or pestle driven by a water wheel. This in turn was superseded by the modern beating engine or Hollander, in- vented by the Dutch in the latter part of the seventeenth century, as described below. The sieve used. in.stead of being made of bamboo, is of wire cloth, with a movable edge or deckel. The workman after forming the sheet removes the deckel, turning the damp sheet onto a sheet of woolen felt. A pile of these sheets, alternate paper and felt, is called a "post,' and is placed in a press to remove the water. The sheets are afterwards hung U]) in a loft to dry. and finished by sizing with glue or gelatin, and smoothed by pressure or calender rolls. Hand-nuidc paper always has four rough edges, while machine- made paper has only two. These are usually trimmed off unless an imitation of hand-made paper is wanted.

Raw Materials. The preparation of any raw material for use as paper stock consists essentially in isolating the cellulose in the form of fibres of as great length as possible. As cellulose is the structural base of all plants, theoretically any plant might furnish the paper- maker with material for his mill. It becomes, therefore, a question of cost of producing the pure cellulose, ami quality of the product. The earliest plant u.sed was the paper mulberry, whose fibres are very easily separated, and a fairly pure cellulose obtained by simply boiling with lye. As this plant does not grow in Europe, it is not used in modern paper-making. The chief material used up to the middle of the nineteenth centurj- was cotton and linen rags. These are already reduced to nearly pure cel- lulose by the processes of textile nianufacture, and cleaning and boiling with an alkali is all that is needed to prepare the stock for pulp. Wood is the raw material of most importance to the paper-maker to-day, and esparto gras.s (alfa) is used in England on a large scale. Straw, waste paper, old rope, jute butts, hemp, etc., are also used. The different processes of reducing the material to a suitable fibre will be considered later.

Peocess of Mauufactube by Macuineby. VV'liether for handmade or for machine-made paper, the preparation of rags for pulp may be divided as follows: (1) Cleaning; (2) boiling; (3) washing: (4) bleaching; {'>) beating or re- ducing to pulp. The preparation of .substitutes for rags is practically the same except that the Imiling process is more drastic, varying with the substance used.

(1) Clcanbifi. — Rags are received at the mill in bales more or less sorted into white, colored, linen, cotton, canvas, etc., but need, for the finer sorts of paper ( in which alone rags are now used at all), a thorough dusting and further sorting by hand. The duster may be of various forms, and removes dust and foreign substances by vigorous mechanical methods. The sorting is done by girls who stand before tables covered with wire screens through which dust and dirt sifts. The girls cut off buttons, rubber (a great curse to the modern paiwr-maker, as it does not bleach and appears in the paper as black specks. Ijesides sticking to rolls and clogging the straining screens ), and other for- eign substances, and sort the rags accurately into different grades. A further dusting and chopping into pieces a couple of inches long make the rags ready for boiling.

(2) BoiUiift. — The rags are packed in a large horizontal boiler, called the 'rotary.' This is provided with manholes for the admission and discharge of the rags and lime, and is mounted on hollow trunnions through which steam is admitted. To clean the rags from all fatty, colored, and non-cellulose impurities, a solution of lime is used, and the rags cooked and slowly rotated under steam ])ressure for several hours, the amount of lime, pressure, and time of boiling varying according to circiunstances. When suffi- ciently cooked, the steam and liquor are blown oft" aiid the rags dumped out by slowly revolv- ing the rotary with the manholes opened. The rags are now of a brown color, and most of the impurities have been sajronified. combining with the lime to form insoluble compounds which can be washed away. or. in the case of colors, reduced to simple colorless compounds.

(3) TTn.sftr'iK?. — The washing or beating en- gine is shown in the cut. It is also called the Hollander. It consists of a wooden or metal tub 10 to l.T feet long, with rounded ends (see cut), in the centre of which is a partition (E)